1. Field of the Invention
The present invention relates to connectors, and more particularly, microwave coaxial connectors having inner and outer conductors.
2. Description of the Related Art
FIG. 1A illustrates a microwave coaxial transmission cable 10 which has two contacts for connecting to a microwave device. One contact is an outer conductor 11 and the other contact is an inner conductor 12. Typically, the outer conductor is used for a ground connection and the inner conductor carries a microwave signal. Both of these conductors form an axial connection with a microwave device. That is, to make a pressure connection with the microwave device, pressure is provided in the direction of the central axis 13 of the inner and outer conductors.
In an axial connection, typically one conductor is firm, while the other conductor is resilient as depicted in FIG. 1B. Typically, a resilient conductor retracts or deforms as axial pressure is exerted between the conductor and another conductor or contact surface. FIG. 1B is a side view of outer conductors 11a-b and inner conductors 12a-b of two microwave coaxial transmission cables 17 and 18, respectively. A firm connection 14 exists between the outer conductors 11a-b while a resilient connection 15 exists between the inner conductors 12a-b. The resilient connection 15 is necessary to absorb the variations in contact surface and angle of contact between the outer conductors 11a-b and inner conductors 12a-b. Also, the resilient connection 15 should generally be maintained at a requisite amount of axial pressure 16 in order to provide constant impedance for any signals transmitted on cables 17 and 18.
The above-identified and incorporated by reference U.S. Pat. No. 5,576,675 entitled "Microwave Connector With An Inner Conductor That Provides An Axially Resilient Coaxial Connection", describes various coaxial connectors having an inner axially resilient conductor, such as a GPC-7 connector.
However, having an outer conductor firm while the inner conductor is resilient may cause a number of problems. First, the outer conductor may damage a housing during the insertion of the connector. FIG. 2 illustrates a conventional N-type connector 20 inserted into housing 21. One of ordinary skill in the art understands that connector 20 includes a large number of components which are not illustrated in order to clearly illustrate the present invention. Connector 20 includes a main component 20b having threads 22. Threads 22 are used to insert connector 20 into housing 21. Connector 20 includes outer conductor 23 and inner conductor 24. Typically, outer conductor 23 is used for a ground and inner conductor 24 is used to carry a microwave signal. Outer conductor 23, in particular surface 26 of outer conductor 23, contacts surface 27 of housing 21 after connector 20 is inserted into housing 21. If outer conductor 23 is used as a ground and housing 21 is grounded, a common ground is formed between conductor 23 and housing 21. Inner conductor 24 is coupled to extendable pin 25. FIG. 2 illustrates connector 20 having an extendable pin 25 rather than an axial resilient pin as described below. Pin 25 overlaps and contacts microstrip 30 rather than forming an axial resilient contact with microstrip 30. After inserting connector 20 into housing 21, pin 25 contacts microstrip 30 on substrate 31 in order to form an electrical connection between microstrip 30 and connector 20, in particular inner conductor 24. In this extendable pin connector 20, contact surface 29 of inner conductor 24 contacts housing 21 at housing surface 28. As described below in regard to the outer conductor, inner conductor 24 may likewise damage housing 21 at housing surface 28 during insertion and lead to damaged internal components and/or erroneous signals.
If inner conductor 24 is axial resilient, pressure is axially exerted between inner conductor 24 (and pin 25) and microstrip 30. Because the inner conductor is axially resilient, the inner conductor 24 retracts or deforms during insertion and does not damage housing 21 at housing surface 28. Further, the inner axially resilient conductor provides a constant pressure and enables relatively constant impedance at the contact position between pin 25 and microstrip 30.
However, outer conductor 26 is not axially resilient. Thus when connector 20 is inserted into housing 21, a force is exerted on housing 21 at the housing surface 27. The insertion force is concentrated on a relatively small housing surface area 27 due to the gap 32 between connector 20 housing 21. This force may be large enough to damage housing 21. This damage to the housing could increase after repeated insertions of connector 20. Electronic components or lines adjacent to housing surface 27 may likewise be damaged. Further, damage to the housing 21 may affect electrical connections between conductors 23 and 24, and housing 21 and microstrip 30, respectively, which may introduce noise or reduce signal strength in a transmitted microwave signal.
Another typical problem encountered with microwave coaxial connectors regards connecting two microwave components. Often a microwave coaxial cable is used to connect two microwave components. However, the coaxial cable length must be selected so as to connect the two components without using excess cable. The excess cable may cause errors or unwanted noise in the microwave signals. Alternatively, if a cable length is selected and cut which is too short, the cable may have to be scraped.
Also, some microwave coaxial connectors for connecting microwave components may require screws, soldering, or ribbon bonding which increases manufacturing costs and complexity. The soldering or ribbon bonding may also affect transmitted signal quality.
Thus, it is desirable to provide a connector which does not damage device housings during insertion which could lead to electronic component damage or erroneous signal transmission. The connector should also provide a predetermined pressure at contact surfaces after insertion in order to maintain constant impedance. Also, a connector for easily connecting microwave components without using costly coaxial cable, screws, soldering or ribbon bonding, is desirable.